How to deal with the money that was contributed to traditional IRA post tax?

Hello everyone,

I have contributed to the traditional IRA with post tax money for several years that has been documented with form 8606. Now I am in retirement and like to take it out or maybe convert to Roth IRA? However, this portion of money was in the same traditional IRA account with the pre tax money I put in earlier when my tax bracket was low. What is best way to get this portion of money and gains out from the tradition IRA? Thanks.